Ophthalmic lenses useful for the correction of presbyopia which incorporate high order aberration correction

ABSTRACT

The invention provides methods for designing ophthalmic lenses, and lenses produced by this method, which lenses corrects both low order and high order wavefront aberrations of the lens wearer&#39;s eyes.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation in part application of U.S.application Ser. No. 11/550,965 filed on Oct. 16, 2006 and claimspriority thereto under 35 U.S.C. 121.

FIELD OF THE INVENTION

The invention relates to ophthalmic lenses that correct presbyopia. Inparticular, the invention provides presbyopia correcting lenses thatcorrect for the wearer's basic refractive error as well as the wearer'shigh order optical aberrations.

BACKGROUND OF THE INVENTION

As an individual ages, the eye is less able to accommodate, or bend thenatural lens, to focus on objects that are relatively near to theobserver. This condition is known as presbyopia. Similarly, for personswho have had their natural lens removed and an intraocular lens insertedas a replacement, the ability to accommodate is absent.

Any number of lens designs have been used in attempt to correct for thewearer's presbyopia. Among the known designs are bifocal and progressivespectacle lenses. Additionally, multifocal contact and intraocularlenses and mono-vision contact lenses are known.

Monovision contact lenses provide one lens that corrects the wearer'sdistance vision acuity and that is worn on the dominant eye or eye thatpredominates for the individuals' distance vision. Additionally, asecond lens that corrects the wearer's near vision acuity and is worn onthe non-dominant eye is provided. These lenses are disadvantageousbecause they only correct for low order optical aberrations, such asdefocus and astigmatism, leaving the lens wearer's higher orderaberrations uncorrected.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The invention provides methods for designing ophthalmic lenses, andlenses produced by the methods, which lenses corrects both low order andhigh order wavefront aberrations of the lens wearer's eyes. The lensesproduced by the methods of the invention are advantageous in that theyprovide improved binocular vision, increased depth of focus and improvedcontrast to the wearer compared to conventional contact lenses used forpresbyopia correction.

In one embodiment, the invention provides a method for producing a pairof ophthalmic lenses for an individual comprising, consistingessentially of, and consisting of the steps of: a.) measuring a firstbasic refractive prescription of a dominant eye of the individual byproviding at least one far fixation target; b.) measuring a second basicrefractive prescription of a non-dominant eye of the individual byproviding at least one far fixation target and measuring a nearrefractive prescription of the non-dominant eye by providing at leastone near fixation target; c.) measuring a first set of high orderwavefront aberrations of the dominant eye by providing at least one farfixation target; d.) measuring a second set of high order wavefrontaberrations of the non-dominant eye by providing at least one nearfixation target; e.) converting each of the first and second sets ofhigh order wavefront aberration measurements to a height difference; andf) using the first basic refractive prescription and height differencefor the dominant eye to provide a first ophthalmic lens and the secondbasic refractive prescription, near refractive prescription, and heightdifference for the non-dominant eye to provide a second ophthalmic lens.

By “lens” is meant a spectacle lens, a contact lens, an intraocularlens, a corneal implant lens, an onlay lens, and the like, orcombinations thereof. Preferably, the lenses of the invention arecontact lenses.

By “basic refractive prescription” is meant the distance power necessaryto correct the distance vision acuity and any cylinder power necessaryto correct astigmatism.

By “near refractive prescription” is meant the near, or add, powernecessary to correct the near visual acuity.

By “dominant eye” is meant the eye that predominates for distancevision.

By “far fixation target” is meant a visual target provided at about 15feet or more from an individual's eye. By “near fixation target” ismeant a visual target at about 30 to about 50 cm from an individual'seye.

In the first step of the invention, a first and a second basicrefractive prescription of the lens wearer is measured for anindividual's dominant and non-dominant eye, respectively, using at leastone far fixation target. Any conventional method may be used for suchmeasurement including, without limitation, use of a phoropter, anautorefractor, trial case lenses, or the like. Alternatively, themeasurement may be carried out by ocular wavefront analysis.

In another step of the invention, a near refractive prescription ismeasured for the individual's non-dominant eye using at least one nearfixation target. Any conventional method may be used for suchmeasurement including, without limitation, use of a phoropter, anautorefractor, trial case lenses, or the like. Alternatively, themeasurement may be carried out using a modified wavefront aberrometercapable of providing near fixation targets.

In yet another step of the method of the invention, the high orderwavefront aberrations of each of the individual's dominant eye andnon-dominant eye are measured at a far fixation target. By “high orderwavefront aberrations” is meant wavefront aberrations other than loworder sphere and cylinder. By “wavefront aberrations” is meant thedifference between the wavefront for spherical aberration, astigmatism,coma, and other distortions emerging from the eye compared to a planewavefront emerging from the eye or a perfect spherical wavefrontconverging on the retina. In the method of the invention, the high orderwavefront measurement for the dominant eye is carried out by providingthe lens wearer at least one far fixation target. The high orderwavefront aberrations for the individual's non-dominant eye is measuredat at least one near fixation target.

Apparatuses for performing the aberration measurements include, withoutlimitation, aberroscopes, devices that measure ocular ModulationTransfer Function by point spread or line spread, or any similar devicesthat measure, estimate, interpolate, or calculate the ocular opticalwavefront. An aberroscope capable of measuring the distance visiontarget is available from Wavefront Sciences, Inc, Albuquerque, N.M. Itis well known in the art how to utilize such an aberroscope, as well asother devices available for aberration measurement, to measure targetsat near distances.

Once obtained, each of the aberration measurements then may bemathematically converted to a height difference thus providing anelevation map above and below a designated mean sphere value, known asthe optical path difference. Correction for the aberrations will beprovided by introduction into the lens design of an optical pathdifference, or aberration inverse filter, that offsets the distortionsdue to the ocular aberrations.

The height differences, along with the basic refractive prescription,and optionally corneal topographic data, are then used to provide a lensfor the wearer. The data may be transformed onto a grid pattern of arectilinear, polar concentric, or spiral format to correspond to themechanism by which the surface of a lens or lens mold may be tooledusing a computer numeric controlled (“CNC”) lathe, direct machining of apolymer button, milling, laser ablation, injection molded insert or thelike or a combination thereof. The required changes in the lens' surfaceelevation or slope to achieve correction of the aberrations may beincorporated onto the lens' front surface, back surface, or acombination thereof.

In one embodiment of the invention, either the front, or convex, or theback, or concave, surface of the lens incorporates the basic refractiveprescription of the lens wearer and, in the case of the non-dominant eyelens, also incorporates the near refractive prescription. The oppositesurface of the lens contains an optic zone that corrects the lenswearer's high order wavefront aberrations. In an alternative embodimentand preferably, either or both of the basic refractive prescriptions andaberration correction may be divided between the front and back surfacesof the dominant eye lens and the basic refractive prescription, nearrefractive prescriptions, and aberration correction similarly may bedivided between the surfaces of the non-dominant eye lens. As yetanother embodiment, the entirety of the refractive prescriptions andaberration correction may be either on the front or back surface of thelens. If corneal topography data is incorporated into the lens design,preferably all of the refractive prescription and aberration correctionis on the front surface and the topographic data is used in the designof the back surface.

For the contact lenses of the invention, in those embodiments in whichboth basic refractive and near refractive power are provided in the formof annular zones, the basic refractive power annular zones preferablyalternate with the near refractive power annular zones. Additionally,cylinder power, prism power or both may be combined with either or bothof the basic and near refractive powers.

In those case in which both near and basic refractive power annularzones are used in the contact lens for the dominant eye, the ratio ofthe lens' optic zone area devoted to the basic and near refractivepowers must be such that more area is devoted to the distance power. Forthe lens of the non-dominant eye, more lens area will be devoted to thenear power. The preferred areas, on a percentage basis, for both thedominant and non-dominant eye lenses are disclosed in U.S. Pat. Nos.5,835,192, 5,485,228, and 5,448,312.

In another embodiment, the invention provides a method for producing apair of ophthalmic lenses for an individual comprising, consistingessentially of, and consisting of the steps of: a.) measuring a firstbasic refractive prescription of a dominant eye of the individual byproviding at least one far fixation target; b.) measuring a second basicrefractive prescription of a non-dominant eye of the individual byproviding at least one far fixation target and measuring a nearrefractive prescription of the non-dominant eye by providing at leastone near fixation target; c.) measuring a first set of high orderwavefront aberrations of the dominant eye by providing at least one farfixation target; d.) measuring a second set of high order wavefrontaberrations of the non-dominant eye by providing at least one farfixation target and measuring a third set of high order wavefrontaberrations of the non-dominant eye by providing at least one nearfixation target; e.) converting the first set of high order wavefrontaberration measurements to a first height difference; f.) calculating anaverage measurement of the second and third sets of measured high orderwavefront aberrations and converting the average measurement to a secondheight difference and g.) using the first basic refractive prescriptionand first height difference for the dominant eye to provide a firstophthalmic lens and the second basic refractive prescription, nearrefractive prescription, and second height difference for thenon-dominant eye to provide a second ophthalmic lens. In yet anotherembodiment of the invention, the high order wavefront aberrations may bemeasured at a near and far fixation target for both of the dominant andnon-dominant eye and, for each eye, the average of these wavefronts maybe calculated. In still another embodiment, the high order wavefrontaberrations are measured at a near and far fixation target for both ofthe dominant and non-dominant eye and, for each eye, the average ofthese wavefronts may be calculated, but the near refractive prescriptionis not measured for the non-dominant eye.

In any of these embodiments, the calculation of the average measurementmay be carried out by any convenient method. For example, thecalculation may be provided by calculating an average of Zernike terms,a weighted average of Zernike terms, or an exponentially weightedaverage of Zernike terms. Alternatively, the average may be calculatedby optimization of image quality metrics, minimization of totalwavefront RMS, selective minimization of selected waverfront terms,optimization of the PSF one-half bandwidth, or optimization of any ofthe Visual Strehl ratios, MTFs or OTFs.

In still other embodiments of the lenses of the invention, the backsurface of one or both of the lenses is matched to the wearer's cornealtopography. For lenses incorporating an inverse topographic elevationmap of the lens wearers' cornea, the corneal topography may bedetermined by any known method including, without limitation, by use ofa corneal topographer. For soft contact lens manufacture, theelevational data initially is applied to a lens model in the unflexedstate. Next, the data is transformed by taking into account the softlens flexure, or wrap, when the lens placed on the eye. Thus, theeffects of both elevation of the cornea and wrap are accounted for whenusing the corneal topographic data. The flexure transformed data thenmay be mapped onto a CNC grid pattern and used to make the lenses ormold tool surface.

Contact lenses useful in the invention may be either hard or softlenses. Soft contact lenses, made of any material suitable for producingsuch lenses, preferably are used. The lenses of the invention may haveany of a variety of corrective optical characteristics incorporated ontothe surfaces in addition to aberration correction and distance and nearoptical powers, such as, for example, cylinder power.

The contact lenses of the invention may be formed by any conventionalmethod. For example, the annular zones formed therein may produced bydiamond-turning using alternating radii. The zones may be diamond-turnedinto the molds that are used to form the lens of the invention.Subsequently, a suitable liquid resin is placed between the moldsfollowed by compression and curing of the resin to form the lenses ofthe invention. Alternatively, the zones may be diamond-turned into lensbuttons.

In another embodiment, the correction above-described is provided oneach lens of a spectacle lens pair. The spectacle lenses may be formedby any known method including, without limitation, grinding of a lensblank, casting, molding, or combinations thereof. In a preferredembodiment, an optical preform having some or all of the basicrefractive prescription for the dominant eye and basic and nearrefractive prescription for the non-dominant eye is used and one or moresurfaces are cast onto the optical preform to provide aberrationcorrection and, optionally, additional basic refractive prescriptionpower.

1. A method for producing a pair of ophthalmic lenses for an individual,comprising the steps of: a.) measuring a first basic refractiveprescription of a dominant eye of the individual by providing at leastone far fixation target; b.) measuring a second basic refractiveprescription of a non-dominant eye of the individual by providing atleast one far fixation target and measuring a near refractiveprescription of the non-dominant eye by providing at least one nearfixation target; c.) measuring a first set of high order wavefrontaberrations of the dominant eye by providing at least one far fixationtarget; d.) measuring a second set of high order wavefront aberrationsof the non-dominant eye by providing at least one near fixation target;e.) converting each of the first and second sets of high order wavefrontaberration measurements to a height difference; and f.) using the firstbasic refractive prescription and height difference for the dominant eyeto provide a first ophthalmic lens and the second basic refractiveprescription, near refractive prescription, and height difference forthe non-dominant eye to provide a second ophthalmic lens.
 2. A lensproduced according to the method of claim 1.